I've managed to center-align a div using the following method:
<div id="container" style="position:absolute; top:0px; left:50%; margin-left:-500px; width:1000px;"></div>
After referring to this solution Trying to center div horizontally and vertically in screen.
However, I encountered an issue where if the client's window width (tested in FF 15.0.1) is smaller than 1000px, the horizontal scrollbar does not allow the left side of the div to be seen.
Is there a pure HTML/CSS solution to address this problem?